There is a stereoscopic image display method using a two-dimensional flat panel display device which combines and displays images from a plurality of visual line directions on an image display surface so as to allow a viewer to selectivelyvisually recognize the image corresponding to the viewpoint position of the viewer.
As a method of displaying a stereoscopic image, there is a twin-lens type which provides displayed images as two images to be observed at the viewpoint positions of a left and right eye, and a multiple-lens type which likewise provides displayed images as multiple images at plural viewpoint positions. Further, there is an integral photography method (IP method) which combines and displays images on an image display surface with respect to numerous visual directions without the consideration of viewpoint positions. Moreover, there is an integral imaging method (II method) applying the integral photography method and using a FPD.
As means for selecting an image, there are known a method to provide sets of optical shielding parts and opening parts in a shape of pin hole or slit in an array form, and a method to provide a lens array or a lenticular lens array on an image display screen with the image location of a lens being at a pixel position. In view of display luminance, the image selection means cause the display luminance to be decreased due to the existence of the shielding parts, and thus it is desirable to use a lens as the means for the image selection.
On the other hand, in order to respond to demands for displaying a two-dimensional image and a stereoscopic image selectively using the same display apparatus, there are approaches to display a two-dimensional image and a stereoscopic image selectively. In a structure using a lens array for image selection means, lenses are structured as a refractive index variable layer for allowing the switching of lens operation. A liquid crystal lens in which the orientation of liquid crystal is controlled in voltage is used as refractive index control achieving means. By the switching of lens operation, it becomes possible to display an image at the original resolution, which is owned by the two-dimensional planar image display apparatus when a two-dimensional image is displayed.
Further, there are increasing demands for selectively displaying a two-dimensional image and a stereoscopic image on a display of a personal computer or a digital terminal. However, in such an apparatus, the viewing distance between the display and a viewer is quite short within a range of about 40 cm to 70 cm. In order to achieve a stereoscopic image via such a short viewing distance, a very wide visual field angle is required. In the current situation, however, a lens, particularly a liquid crystal lens, that can achieve such a wide visual field angle has not been achieved yet.